Steady-state Reynolds-stress simulations of a stirred tank

Abstract

This report describes steady-state predictions of the turbulent flow generated by a disc turbine inside a baffled tank. The impeller has been modeled by prescribing experimental flow profiles in the outflow of the impeller. The effects of these boundary conditions and of the grid size and turbulence model have been investigated. The turbulence models also have been investigated in a simpler channel-flow situation to asses the effect of different modeling parameters. No grid independent solutions could be found. Still, one grid has been chosen on which accurate and efficient simulations could be made. On this grid, simulations as to. the effect of the impeller boundary conditions showed that using the correct mean velocity profiles is important. Using appropriate dissipation rate and kinetic energy profiles is important to model the turbulence correctly. The effect of errors in the Reynolds stress cross terms was found to be small. Simulations as to the channel flow showed that the k-e and Reynolds stress models can predict the mean velocity and kinetic energy correctly. The error found in the predicted anisotropy tensor was found to be significant. This error was related to the boundary conditions. In the stirred tank, the k-e model was found to provide better predictions inside the impeller outflow, while the Reynolds stress model predicts the flow inside the bulk region more accurately.Kramers Laboratorium voor Fysische TechnologieApplied Science